Certain clinical and morphologic features are described in three patients who developed severe aortic regurgitation after aortic valve replacement. The regurgitation, fatal in two of the three patients, resulted from long sutures or their knots or both overhanging the metallic ring of the prosthesis preventing complete seating of the occluder. In one patient, simply cutting the overhanging suture eliminated the aortic regurgitation. The problem of suture overhang appears more likely to occur when aortic valve replacement is carried out in patients with relatively small aortic roots. Before closing the aortotomy after aortic valve replacement, it is advisable to move the occluder back and forth to make sure its movement, and specifically, its ability to seat completely, is not limited by sutures which are too long.